Several processes are reported for the hydrolysis of pyridine nitriles to amides. The conversion of nitriles to amides has been achieved by both chemical and biological means.
Generally, it is known that microorganisms containing nitrile hydratase convert nitriles to the corresponding amides. European patent No. 188316 describes a process for the preparation of nicotinamide starting from 3-cyanopyridine using microorganisms of the genus Rhodococcus, Arthrobacter or Microbacterium. 
European patent No. 307926 describes the conversion of 3-cyanopyridine to nicotinamide by means of microorganisms of the species Rhodococcus rhodochrous J1.
European patent No. 362829 reported the addition of urea or a urea derivative to the culturing medium as an inducer, in order to increase the specific activity of the microorganisms containing nitrile hydratase.
U.S. Pat. No. 5,827,699 discloses a process for the preparation of aromatic amides starting from the corresponding nitriles by means of microorganisms of the species Rhodococcus rhodochrous M33.
The disadvantage of most of these biological processes is that most of these micro-organisms have only a low activity for the conversion of cyanopyridine to pyridine amide. Further, some of the microorganisms are colored and accordingly a discoloration of the product takes place. In addition, these microorganisms have low heat stability and are inhibited, for example, by the substrate nitrile pyridine.
Several chemical processes are also reported for the preparation of pyridine amide compounds. Japanese Patent No. 93-206579 and European Patent No. 85-306670 describes the use of a modified Raney Nickel catalyst for the hydrolysis reaction.
U.S. Pat. No. 2,471,518; U.S. Pat. No. 4,721,709 and U.S. Pat. No. 4,314,064 discloses the hydrolysis of 3-cyanopyridine in the presence of sodium hydroxide. Rossa and Smith in Chemical Engineering Science, 1975, 35, 330 reported the use of magnesium oxide catalyst for the hydration reaction.
However, these reported processes have several disadvantages, for example, low yield, high reaction temperature and high alkali concentration. Moreover, high amount of nicotinic acid is also produced along with nicotinamide in these processes.
British Patent No. 1133013 describes the catalytic hydration of nitriles by manganese dioxide, prepared by the redox method using potassium permanganate and manganese sulphate in an alkaline medium. The hydration of 3-cyanopyridine/4-cyanopyridine is conducted using a catalyst in the mole ratio of 2.16:1. The yield reported is only 79.28 mole %. The main drawbacks of the process are that the yield is less, it is not eco-friendly and the amount of catalyst per mole of the feed for conversion is quite high.
U.S. Pat. No. 4,008,241 discloses the production of nicotinamide from 3-cyanopyridine by aqueous ammonia solution. The reaction temperature is 90-150° C., the reaction time is 4-8 hours and the ammonia concentration is 3-8 molar. The maximum conversion of 3-cyanopyridine is about 70%. However, this process involves multi-step separation of product from hydrolysis effluent which contains nicotinamide, ammonia, unconverted 3-cyanopyridine and ammonium nicotinate thereby making it less cost effective and tedious to get the pure product.
Sakai et al. in Bull. Chem. Soc., Japan, 1967, 40, 1660 have reported preparation of nicotinamide and isonicotinamide using nickel oxide as a catalyst. However, the catalytic activity as well as yield is low.
Indian patent No. 194989; U.S. Pat. Nos. 7,345,176 and 7,455,827 also discloses a process for the preparation of manganese dioxide catalyst useful for the preparation of nicotinamide and isonicotinamide. Manganese dioxide catalyst is prepared by redox method using potassium permanganate and manganese chloride in neutral medium to obtain the reaction mixture and then continuously stirring the obtained reaction mixture, filtering and drying to obtain the manganese dioxide catalyst. The yield of nicotinamide reported is 91.8 mole % and selectivity is 100%. However, when these processes were conducted in laboratory, no reproducible results were obtained. Moreover, no mention of niacin formation at reaction stage or at final product, no recycling during catalyst preparation or during amide preparation makes the process economically unattractive. Further, concentration of 3-cyanpoyridine in water is very low resulting into low productivity of niacinamide.
Chinese patent No. 101851194 discloses a method for the preparation of niacinamide with high yield and selectivity by dissolving 3-cyanopyridine in ethyl alcohol, water and catalyst at 80-100° C. in 6-10 h reaction time to give 99.7% niacinamide, 0.3% nicotinic acid. However, the main draw backs of this invention is the use of higher amount of catalyst (20% w/w of 3-cyanopyridine); concentration of 3-cyanopyridine in solvent is only 25% which leads to lower productivity.
Thus, the processes disclosed in the prior art have several disadvantages to be used for the commercial manufacturing of pyridine carboxylic acid amides. For example, most of the processes results in the formation of pyridine carboxylic acid, removal of which is conventional and cumbersome resulting into low recovery of product. The prior art processes involves multi-step, capital intensive purification process, which also results in generation of large amount of effluents, consequently making the process costly and uneconomical. Further, the processes can be used for producing small batches of the desired products in low yield and at higher costs, hence making the processes unsuitable for large-scale production.
The catalysts reported in the prior art, have number of serious drawbacks. These catalysts reported in the prior art quickly lose activity making it necessary to carry out frequent reactivation or use of new catalyst. In some of the prior art though the overall yield is increased but the product obtained is impure thereby requiring several steps for extraction and tedious isolation to obtain the desired products.
Thus, there is a need to develop a process for the production of pyridine carboxylic acid amides and catalyst for the process at industrial scale, which can improve the yield, selectivity, quality and minimize effluent generation to greater extent.
Therefore the present invention provides a solution to the aforesaid problems of the prior arts overcoming the above drawbacks and disadvantages by employing an improved catalyst and a cost effective and eco-friendly process for the industrial scale production of pyridine carboxylic acid amides.